When a decorative adhesive film is adhered to an adherent, a volume of an air is trapped between the adhesive layer and adherent, so that the appearance of the decorative film tends to be worsened. To prevent the trapping of air, considerable skill is required to adhere the adhesive film to the adherent, and a relatively large amount of work and a long time are required for adhering.
Various attempts to avoid the trapping of air are disclosed in the following publications, grouped into two approaches as follows.
1) Adhesive film comprising a single layer structure type adhesive layer:
(a) JP-A-6-287525 discloses an adhesive film having a structure in which an adhesive layer comprising elastic microspheres and an adhesive is formed on a surface of a substrate film. Such structure enables the removal of the bubbles between the adhesive and adherent even during contact adhering. The adhesive layer contains the elastic microspheres having a relatively large volume average diameter of 100 to 300 .mu.m and achieves high peel resistance. However, a substrate film surface becomes uneven after the adhesive film is adhered, and it is difficult to maintain good appearance.
(b) A repeelable adhesive film is disclosed in JP-A-8-113768 to have a structure in which an adhesive layer comprising elastic microspheres and an adhesive is formed on a surface of a substrate film. This adhesive layer contains the elastic microspheres having a relatively small volume average diameter of 10 to 100 .mu.m unlike publication (a). Thus, the substrate film surface does not become uneven, and the film has good appearance. However, it is difficult to increase the peel resistance by the use of the elastic microspheres having the relatively small diameter. If elastic microspheres having a further smaller diameter (less than 10 .mu.m) are used to increase an adhesion area and peel resistance, good bubble escapability is not achieved. If an amount of the adhesive in the elastic microsphere layer increases, the bubble escapability is lowered although the peel resistance increases.
(c) JP-A-7-53930 discloses a protective adhesive film having a structure in which an adhesive layer comprising adhesive microspheres is formed on one surface of a substrate film. When this protective film is adhered to an adherent using a laminator, it can be adhered with leaving no bubble at an adhesive interface. However, this publication does not disclose any means for escaping bubbles, high peel resistance and good appearance of the film surface at the same time. Furthermore, this publications does not describe that the adhesive microspheres form clusters.
2) Adhesive film comprising a double layer structure type adhesive layer:
(a) A repeelable adhesive tape or sheet disclosed in JPU-5-72946 is characterized in that it comprises a substrate film, a viscoelastic layer formed on the substrate, and an adhesive layer which contains polymeric microspheres and is formed on said viscoelastic layer. This enables the good adhesion of the tape or sheet to an adherent having an uneven surface such as a corrugated fiberboard, and repealing while preventing spontaneous peeling off. Since the polymeric microspheres having a relatively small average particle size in the range between 1 and 10 .mu.m are used to impart the repeelability to the film, it is difficult to remove the bubbles between the adhesive layer and the adherent. Since the polymeric microspheres comprise a non-adhesive type polymer such as polymethyl methacrylate, an adhesion force Is low, and the film may be spontaneously peeled off when it is used outdoors. Since the viscoelastic layer absorbs the unevenness on the surface when the adhesive film is adhered to the adherent, it should have a flowability such that it can be easily deformed by pressing. However, this Utility Model application does not describe any degree of the viscoelasticity of the layer,
(b) A position-adjustable adhesive tape disclosed in JPA-3-181578 has a structure that a plurality of nonadhesive materials or glass beads are distributed with a constant interval on a surface of a pressure sensitive adhesive layer. Since such a structure prevents the direct contact between the adherent and adhesive, the layer has slipping properties, and the good bubble escapability is attained when the film is temporarily adhered. However, after contact adhering, since the beads are embedded in the adhesive, the film is strongly adhered to the adherent but loses the bubble escapability, and it is difficult to remove the bubbles between the adhesive and the adherent during contact adhering.